1. Field of the Invention
The present invention relates generally to a coaxial microstripline transducer for use as, for example, a coaxial connector, and more particularly, to a coaxial microstripline transducer comprising an inner conductor having a center conductor portion arranged in a recess portion which opens upward, and an outer conductor arranged apart from the center conductor portion.
2. Description of the Prior Art
A coaxial microstripline transducer shown in FIGS. 12 to 15 has been conventionally known. FIG. 12 is a plan view illustrating a coaxial microstripline transducer, FIGS. 13 and 14 are respectively a cross-sectional view taken along a line V--V shown in FIG. 12 and a cross-sectional view taken along a line VI--VI shown in FIG. 12, and FIG. 15 is a bottom view illustrating the coaxial microstripline transducer.
In this coaxial microstripline transducer, a cylindrical recess portion 71a which opens upward is formed in a resin case 71 made of insulating resin. In the recess portion 71a are a center conductor portion 72 having a cylindrical shape made of a metal material and a first conductor portion 73 in the shape of a part of a cylindrical curved surface. A lower end of the center conductor portion 72 is connected to a terminal portion 74 made of a metal material. The terminal portion 74 is formed so as to lead to a lower surface via a side surface of the resin case 71 in order to connect the microstripline transducer to a connecting land (not shown) on a substrate. That is, the center conductor portion 72 and the terminal portion 74 constitute an inner conductor of the microstripline transducer.
On the other hand, the first conductor portion 73 is connected to a second conductor portion 75. The second conductor portion 75 is formed so as to lead to the lower surface via the side surface of the resin case 71 in order to connect the microstripline transducer to a connecting land (not shown) on the substrate. The first conductor portion 73 and the second conductor portion 75 constitute an outer conductor of the microstripline transducer. In addition, embedded metal parts 76 are formed on the lower surface of the resin case 71 in order to increase stability and bond strength, when the microstripline transducer is mounted on a substrate or the like.
The above-described inner conductor and outer conductor are respectively formed by working a metal plate or a metal wire in accordance with a working method such as press working. The above-described coaxial microstripline transducer is constructed by mounting the metal members on the resin case 71 which is a molded resin product.
In the above-described microstripline transducer, the outer conductor comprising the first conductor portion 73 and the second conductor portion 75 are incorporated into the resin case 71 and the second conductor portion 75 is folded along the lower surface of the resin case 71. However, such an assembly operation is very difficult because the resin case 71 is small. That is, the plane dimensions of the resin case 71 are small, approximately 4 mm.times.4.5 mm, for example, so that the operation which includes passing the outer conductor having a complicated shape from the inside of the recess portion 71a to the outer side surface of the resin case 71 and further pulling the same out to the lower surface of the resin case 71 is very difficult. Particularly, there is a strong demand for miniaturization of the microstripline transducer, as with other electronic components. However, the smaller the dimensions of the microstripline transducer are, the more difficult the above described assembly operation is. Consequently, the manufacturing processes are complicated, and the manufacturing cost is increased.
Furthermore, in the above-described coaxial microstripline transducer, the terminal portion 74 of the inner conductor, the second conductor portion 75 of the outer conductor, and the embedded metal parts 76, which are arranged on the lower surface of the resin case 71, as shown in FIG. 15, are relatively small. The terminal portion 74, the second conductor portion 75, and the embedded metal parts 76 are soldered to a wiring pattern or to connecting lands on the substrate, to mount the microstripline transducer on the substrate. Because the base areas of the terminal portion 74, the second conductor portion 75, and the embedded metal parts 76 are relatively small, sufficient soldering strength (mounting strength) cannot be obtained.
It has been suggested to increase the areas of the parts located on the lower surface of the resin case 71, namely the terminal portion 74, the second conductor portion 75, and the embedded metal parts 76, to thereby increase the soldering strength. However, an attempt to increase the soldering areas causes a heavy load to be applied to the resin case 71 in folding the terminal portion 74 and the second conductor portion 75 along the resin case 71, resulting in the possibility of damaging the resin case 71. Consequently, the soldering areas of the terminal portion 74, the second conductor portion 75, and the embedded metal parts 76 cannot be greatly increased in size.
Additionally, as shown in FIG. 13, the inner conductor, comprising the center conductor portion 72 and the terminal portion 74, is mounted on the resin case 71 by insert molding. However, the terminal portion 74 is folded along the side surface and the lower surface of the resin case 71 after the insert molding. Consequently, there is a limit on the amount the thicknesses T1 and T2 (see FIG. 13) of bottom parts of the resin case 71 can be decreased, so that the products are prevented from being reduced in height.